1. Field of the Invention:
The invention has to do with the vacuum distillation of a sponge refractory metal product, such as zirconium and/or hafnium sponge, that has been produced from a metal tetrachloride by the use of magnesium metal as a reductant, the sponge metal product containing a residual amount of magnesium chloride in its pores as an impurity.
2. Description of the Prior Art:
In the production of various refractory metals in sponge form, such as zirconium, hafnium, titanium, and uranium, from tetrachlorides of such metals, magnesium metal is normally utilized as a reductant. This produces a considerable quantity of magnesium chloride, residual amounts of which are difficult to remove from the pores of the sponge metal. Retention of even a relatively small amount of the magnesium chloride in the sponge metal product means that an impure final metal product is obtained in the subsequent processing of the sponge metal.
The usual way of ridding the sponge metal of magnesium chloride is to heat the sponge metal to magnesium-chloride-vaporizing temperature in a vacuum distillation furnace. However, it has been found that often the furnace charge of the sponge metal must be recycled through the vacuum furnace several times before the required high purity of metal desired by subsequent processing is assured.